Laminated ball bat

ABSTRACT

A ball bat typically used in playing the game of baseball or softball is constructed of an inner layer bounded by first and second outer layers. The inner layer typically contains four inner lamina bonded together, while the first and second outer layers typically contain a single outer lamina. The inner laminas from the medial portion of the barrel of the bat, as well as the handle portion. The outer laminas form lateral portions of the barrel of the bat, and are gently tapered toward the handle of the bat. The thickness and relative position of each lamina is related to the results of non-destructive testing of the wood forming that lamina.

CROSS-REFERENCES

There are no applications related to this application filed in this orany foreign country.

BACKGROUND

Ball bats made out of glued laminations are known, such as thatdisclosed by U.S. Pat. No. 5,490,669. Such bats provide a number ofadvantages, including particularly increased strength resulting in partfrom the 180 degree rotation of adjacent plies. Such rotation causes thewood grain in adjacent plies to be substantially mirror images. As aresult, the wood throughout the bat is more uniform, thereby decreasingthe likelihood of a weak spot, which tends to result in a stronger bat.

Additionally, as a result of the cuts made to separate the plies, the"inside" of the wood is revealed. This can result in the observation ofweak spots, allowing replacement with stronger wood. However, knownlaminated bats have not addressed the issue of nondestructive testing ofeach of the lamina used to make the bat As a result, the use ofsubstandard lamina is possible. As a result, it is the case that knownlaminated bats are constructed of individual lamina arranged inlocations within the bat that have stress levels that are incompatiblewith that particular lamina's strength level.

As seen above, the use of glued lamina in bat construction generallyresults in a stronger bat. However, since known laminated bats have usedlamina having a uniform thickness, the resulting increase in strength isuniform throughout the bat, rather than being particularly directed tothose areas of the bat that are more likely to break. This is becausethe specific area of breakage in most bats is an area generally locatedbetween the ball player's grip and the impact location of the ball, i.e.in a region between the handle and barrel. This implies that to decreasethe likelihood of a bat breaking, certain "weak-link" areas need to bestronger, while other areas of existing bats are already unlikely tobreak Known laminated bats have not fully addressed the issues ofselectively strengthening the weaker areas of a bat.

SUMMARY

The present invention is directed to an apparatus that satisfies theabove needs. A novel ball bat and method of manufacture that includesthe use of glued laminations is provided wherein non-destructive testsare performed on each lamina used in the construction, and also includesa test of the entire finished bat. Laminas of different thicknessesallows a targeted increase in the strength of the weaker areas of thebat without adding undue cost to the construction.

A preferred version of the laminated ball bat includes a handle end anda barrel end, and further includes:

(A) An inner layer has opposed first and second elongate inner layersurfaces and is cut from one or more initial laminas having ends spacedlengthwise and grain running lengthwise between the first and secondends of the initial lamina. In a preferred embodiment, the inner layerincludes:

(a) At least two inner laminas bonded together, each of the at least twolamina having opposed first and second elongate inner lamina surfaces.In a typical application, the inner layer provides four inner laminasbonded together, having an aggregate thickness of about one inch.

(B) First and second outer layers are carried by the first and secondelongate inner layer surfaces, respectively. In general, the thicknessesat the thickest points of the inner layer and first and second outerlayers are all approximately equal. The first and second outer layersshould be cut from initial laminas having first and second ends spacedlengthwise and grain running lengthwise between the first and secondends.

(C) In the preferred embodiment of the invention, non-destructivetesting graded the initial laminas used to form the inner layer asstronger than the initial laminas used to form the outer layer. Thenon-destructive testing may include testing of the modulus ofelasticity, specific gravity, damping ratio, visual inspection and theultrasonic stress wave propagation time, among other tests.

A preferred version of the method of making the ball bat of theapparatus portion of the invention, includes the steps of:

(A) Cutting a number of initial lamina from initial blocks of wood.

(B) Grading each of the initial lamina for density.

(C) Segregating the initial lamina, whereby the higher density initiallaminas are earmarked as candidates for possible use in the inner layerand the lower density initial laminas are earmarked for use in the outerlayer.

(D) Cutting the initial lamina candidates for use in the inner layerinto inner lamina, typically 0.33 inches thick, and planing those innerlamina to the preferred thickness, typically 0.25 inches.

(E) Non-destructively testing each of the inner lamina to determine oneor more of the following, including the modulus of elasticity, specificgravity and damping ratio.

(F) Grading each of the inner lamina on a pass-or-fail basis using theresults of the non-destructive testing, and a corresponding assignednumerical value.

(G) Assembling an inner layer by bonding together a plurality of passinginner lamina. The inner layer therefore has the same length and width aseach inner lamina, but a thickness equal to the aggregate thickness ofall of the inner laminas bonded together.

(H) Planing lower density initial laminas to a precise thickness,thereby forming outer laminas.

(I) Attaching at least one of the outer laminas to either side the innerlayer, thereby forming a laminated billet.

(J) Turning the laminated billet on a lathe or similar machine, therebyforming and contouring the barrel and handle portions of a ball bat.

It is therefore a primary advantage of the present invention to providea novel ball bat and method of manufacture that includes the use ofglued laminations, including an inner layer having opposed elongatesurfaces bonded to first and second outer layers, the inner layerforming the bat's handle and the center portion of the bat's barrel, andwhere the inner layer is typically formed of wood of a superior gradeand strength to that of the outer layer, and particularly having asuperior modulus of elasticity.

Another advantage of the present invention is to provide a novel ballbat and method of manufacture that includes the use of gluedlaminations, wherein an inner layer is formed of a plurality of thinnerinner laminas and each outer layers is typically formed from a singlethicker outer lamina, thereby focusing the strength improvement in thehandle and area between the handle and barrel that is most likely tobreak.

Another advantage of the present invention is to provide a novel ballbat and method of manufacture that includes the use of gluedlaminations, wherein the initial laminas to be used in the inner layerare cut into thinner inner lamina which are then individually graded bynon-destructive testing to determine their suitability for use, therebyresulting in an inner layer having substantial strength improvement

A still further advantage of the present invention is to provide a novelball bat and method of manufacture that includes the step of a staticbending test of the completed ball bat to determine the modulus ofelasticity and overall quality of the final ball bat.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1 is an isometric view of an initial block of wood, suitable foruse in making a ball bat;

FIG. 2 is an isometric view of three initial lamina, having been cutfrom the initial block of wood;

FIG. 3 is an isometric view of an outer lamina, having been formed froman initial lamina by planing its surfaces to exact dimensional values;

FIG. 4 is an isometric view of three inner lamina having been cut froman initial lamina, but not yet having been planed to exact dimensionalvalues;

FIG. 5 is an isometric view of the laminated billet, having an innerlayer formed of four inner lamina and having first and second outerlayers, each outer layer having a single outer lamina; and

FIG. 6 is an isometric view of a laminated ball bat, having been turnedfrom the laminated billet of FIG. 5.

DESCRIPTION

Referring in generally to FIGS. 1-5, a ball bat 10 having a structureconsistent with construction in accordance with the method and structureof the invention is seen. The ball bat is suitable for use in playingthe game of baseball or softball. The ball bat is constructed of aninner layer 50 bounded by first and second outer layers 70. The innerlayer typically contains four inner lamina 60 bonded together, while thefirst and second outer layers typically contain a single outer lamina80. The inner laminas 60 form the handle 20 and the medial portion ofthe barrel of the bat. The outer laminas 80 form lateral portions of thebarrel 30 of the bat, and are gently tapered toward the handle of thebat. The thickness and relative position of each lamina is related tothe results of non-destructive testing of the wood forming that lamina.

In a preferred method of construction, an initial block of wood 40 iscut into initial laminas 42 having a size of approximately 38" (inlength) by 3" (in width) by approximately 1" (in thickness). Thepreferred wood to be used is a select grade of northern white ash.

The length of the initial wood laminas 42 must be selected to besomewhat greater than the length of the bat to be manufactured. Thewidth must be greater than or equal to the diameter of the widest pointof the barrel of the bat to be manufactured. The thickness should beselected to be slightly greater than or equal to the thickness of theouter laminas 80. In a preferred embodiment, the outer laminas may be7/8 inch. As a result, the thickness of the initial laminas should beapproximately 1 inch. The thickness of the outer laminas will be reducedsomewhat by planing, and later by the lathe in later steps in themanufacturing process, as will be seen.

Each of the initial laminas is then graded according to some indicatorof quality, such as density. Another indicator of quality that couldalternatively be used is a measurement of the modulus of elasticity.

Having determined the density or other indicator of quality of eachindividual initial lamina pieces, the initial lamina are then segregatedinto two groups. A first group, having relatively lower density or otherindicator of quality, will be segregated for use in the construction ofthe lateral portions of the bat's barrel, and will be referred to asouter lamina. A second group, having relatively higher density or otherindicator of quality, will be segregated for use in the construction ofthe bat's handle and the central areas of the bat's barrel, and will bereferred to as inner lamina. In a preferred version of the invention,wood having a density of less than 44 pounds per cubic foot is put intothe first group, while wood having a density of greater than 44 poundsper cubic foot is put into the second group, although this targetdensity can be adjusted, as desired.

The higher density initial lamina, having been segregated for use in theconstruction of the handle and central portion of the barrel, shouldthen be cut again, thereby creating a number of inner lamina 60. Thecutting process typically reduces the thicknesses of the inner lamina toapproximately 0.30 inches. Typically, where each of the initial laminasare 1" in thickness, three inner laminas may be cut from each initiallamina. Having cut three inner laminas 60 from one initial lamina, theinner laminas are then planed to a thickness of 0.25 inches in apreferred embodiment.

In a preferred embodiment of the invention, four inner lamina 60 areused in the construction of the inner layer 50, which forms the handleand inner barrel portion of the bat. Where four inner lamina are used,each typically has a thickness of 0.25 inches. However, a greater orlesser number of inner laminas, each having a greater or lesserthickness could be substituted. In a preferred embodiment, the totalthickness of the inner layer 50, which includes of all of the innerlamina 60 used in the construction of the handle and central barrelportion of the ball bat, is approximately 1.0 inch. In general, use of agreater number of inner lamina will result in each lamina being thinner.

In the preferred embodiment of the invention, each individual innerlamina 60 is then mechanically graded to determine quality. Moreparticularly, in the preferred version of the invention, numericalvalues for three criteria are obtained, including: (1) the modulus ofelasticity; (2) the density; and (3) the damping ratio. In analternative embodiment, one or more of the criteria may be evaluated.

The modulus of elasticity is a fundamental measure of the resiliency ofthe wood, and it also is correlated to its strength. The density of woodis correlated to wood strength and stiffness, while the damping ratio isanother indicator of wood quality.

In the preferred embodiment, the grading process for determining themodulus of elasticity, density, sonic propagation time and damping ratioinvolves the use of an automated non-destructive testing system, such asthe Metriguard model 2600FX machine used in conjunction with theMetriguard 340 Transverse Vibration E-Computer. Both machines are madeby Metriguard, Inc., of P.O. Box 399, Pullman, Wash. 99163.

Using the measured values for the modulus of elasticity, the density,the damping ratio, and ultrasonic stress wave propagation time, anestimate of the overall relative strength of each lamina is thencalculated, and the lamination grade is output automatically. Thegrading process is typically evaluated in a pass or fail manner, whichwill result in the elimination of some inner lamina which do not meetquality control standards.

Inner lamina 60 are then selected from among those passing the testingfor construction of the inner layer 50, which will form the ball bat'shandle and an inner portion of the barrel portion of the bat. Theselection process typically involves picking four 0.25 inch thick innerlamina. Adjacent first and second elongate inner lamina surfaces 62, 64of consecutive selected inner lamina 60 are then bonded together bymeans of an adhesive, typically using a vise during the drying process,thereby forming the inner layer 50.

An outer layer 70 is then attached to the first and to the secondelongate inner layer surfaces 52, 54 of the inner layer 50. In apreferred embodiment, each outer layer 70 includes a single outer lamina80. In an alternative embodiment, the outer layer 70 may be formed fromtwo or more outer lamina 80 bonded together. The outer lamina 80 areformed by planing an initial lamina 42, earlier segregated into thefirst group for use in the lateral portions of the bat's barrel, from astarting thickness of 1 inch to a finished thickness 7/8 inches.

The inner layer 50, together with outer layers 70 bonded to the firstand second elongate inner layer surfaces 52, 54, form a laminated billet44, typically having a length of approximately 38" and a 3" width and a3" thickness (due to the cumulative thicknesses of the inner and outerlaminas).

The laminated billet 44 is then turned on a lathe in a manner thatcontours the bat to form a handle, barrel and transition between thetwo. The manner in which a bat may be formed from a laminated billet isknown and described in U.S. Pat. No. 5,490,669 issued Feb. 13, 1996 toMerlin L. Smart, which is hereby incorporated in its entirety byreference.

The ball bat is then subjected to a static bending test. A staticbending test determines the stiffness of the entire finished ball bat ina non-destructive manner. A static bending test may be performed by amachine such as the Model 440 Static Bending Tester, by Metriguard,Inc., of P.O. Box 399, Pullman, Wash. 99163. The static bending testprovides a laboratory measurement of flatwise bending modulus ofelasticity (E) of the completed ball bat. The output of this test isused in a pass or fail manner to grade the ball bats as to whether theywere adequately manufactured with respect to a quality assuranceprogram.

The previously described versions of the present invention have manyadvantages, including a primary advantage of providing a novel ball batand method of manufacture that includes the use of glued laminations,including an inner layer having opposed elongate surfaces bonded tofirst and second outer layers, the inner layer forming the bat's handleand the center portion of the bat's barrel, and where the inner layer istypically formed of wood of a superior grade and strength to that of theouter layer, and particularly having a superior modulus of elasticity.

Another advantage of the present invention is to provide a novel ballbat and method of manufacture that includes the use of gluedlaminations, wherein an inner layer is formed of a plurality of thinnerinner laminas and each outer layers is typically formed from a singlethicker outer lamina, thereby strengthening the handle and area betweenthe handle and barrel that is most likely to break.

Another advantage of the present invention is to provide a novel ballbat and method of manufacture that includes the use of gluedlaminations, wherein the initial laminas to be used in the inner layerare cut into thinner inner lamina which are then individually graded bynon-destructive testing to determine their suitability for use, therebyresulting in an inner layer having substantial strength.

A still further advantage of the present invention is to provide a novelball bat and method of manufacture that includes the step of a staticbending test of the completed ball bat to determine the modulus ofelasticity and overall quality of the ball bat

The invention resides not in any one of these features per se, butrather in the particular combination of all of them herein disclosed andclaimed and it is distinguished from the prior art in this particularcombination of all of its structures for the functions specified.

Although the present invention has been described in considerable detailand with reference to certain preferred versions, other versions arepossible. For example, the thickness and number of the inner and outerlaminas in the inner and outer layers is somewhat arbitrary, and couldbe altered while still keeping within the scope of the invention, whichincludes the use of thinner inner lamina in the handle and centralbarrel portions of the bat and thicker outer lamina used in the outerbarrel portions. Therefore, the spirit and scope of the appended claimsshould not be limited to the description of the preferred versionsdisclosed.

In compliance with the U.S. Patent Laws, the invention has beendescribed in language more or less specific as to methodical features.The invention is not, however, limited to the specific featuresdescribed, since the means herein disclosed comprise preferred forms ofputting the invention into effect. The invention is, therefore, claimedin any of its forms or modifications within the proper scope of theappended claims appropriately interpreted in accordance with thedoctrine of equivalents.

What is claimed is:
 1. A laminated ball bat having a handle end and abarrel end, the laminated ball bat comprising:(A) an inner layer havingopposed first and second elongate inner layer surfaces, the inner layercut from a first initial lamina having first and second ends spacedlengthwise with grain running lengthwise between the first and secondends, the inner layer comprising:(a) four inner laminas bonded together,each of the four lamina having a thickness of approximately 0.25 inches,and each of the four lamina having passed a first pass or fail gradingprocess for the modulus of elasticity, density and damping ratio, andeach of the four lamina having opposed first and second elongate innerlamina surfaces; (B) first and second outer layers having opposed firstand second elongate outer layer surfaces, the first and second outerlayers carried by the first and second elongate inner layer surfaces,respectively, the first and second outer layers cut from second initiallaminas having passed a second pass or fail grading process, the secondinitial laminas also having first and second ends spaced lengthwise withgrain running lengthwise between the first and second ends; and (C)wherein the first initial laminas used to form the inner layer arestronger than the second initial laminas used to form the outer layer,as determined by non-destructive testing methods.